Heretofore, it has been known to employ graphic arts photographic elements which are low in photographic speed and are intended to be used under bright safelight or even ordinary room-light conditions. Such materials are referred to herein as "room-light-handleable" emulsions, elements, or materials. The term "room-light-handleable" is intended to denote that the material can be exposed to a light level of 200 lux for several minutes without a significant loss in maximum density. typically, such materials require on the order of 10,000 ergs per square centimeter for D.sub.min exposure.
In the field of graphic arts, it is well known to incorporate soluble dyes in an overcoat layer of a photographic element to absorb unwanted light and decrease photographic speed so that longer exposure times can be used. This technique is useful in providing high-contrast room-light-handleable black-and-white photographic elements. However, soluble dyes tend to migrate to other layers of the element such as the silver halide emulsion layer. When light passes through the emulsion layer, it encounters a concentration gradient of dye and thus more light is absorbed as it travels through the emulsion layer. The bottom of the emulsion layer encounters much less light than the top and, as a result, the contrast is reduced. Another problem is that the degree of migration of soluble dye that occurs in a photographic element is random. Accordingly, random speed variability can occur, depending on how much dye is concentrated at a particular position in the emulsion layer.
Matting agents are often used in photographic elements to provide a rough surface to the element, which is often desirable. Matting agents can provide an irregular surface to a photographic element, thereby permitting sufficient surface roughness to allow retouching or writing on the surface of the element. Surface roughness can also be desirable to prevent the surface of the photographic material from sticking to an adjacent surface and can provide a desired coefficient of friction to allow for use in apparatus for rapid handling and transport of the photographic material. Additionally, matting agents can help prevent the formation of Newton's rings when printing and enlarging because the area of contact of the surface of the photographic material with another material is relatively small due to the spacing effect of the matting agent. In lithographic photographic processes involving juxtaposing an unexposed photographic element with an original image that is desired to be copied, or an image-containing processed film element with a printing plate to impose an image on the plate, roughness on the surface of the film element imparted by a matting agent allows for relatively rapid vacuum draw-down between the film element and the original or plate.
Matting agents are usually present in a separate, overcoat layer of a photographic element, although they can be incorporated in a lower layer such as an emulsion layer or interlayer as long as they impart roughness to the element. Examples of organic matting agents are particles, often in the form of beads, of polymers such as polymeric esters of acrylic and methacrylic acid, e.g., poly(methylmethacrylate), cellulose esters such as cellulose acetate propionate, cellulose ethers, ethyl cellulose, polyvinyl resins such as poly(vinyl acetate), styrene polymers and copolymers, and the like. Examples of inorganic matting agents are particles of glass, silicon dioxide, titanium dioxide, magnesium oxide, aluminum oxide, barium sulfate, calcium carbonate, and the like. Matting agents and the way they are used are further described in U.S. Pat. Nos. 3,411,907 and 3,754,924.
It is a common practice in the photographic art to coat more than one layer of a photographic element in a single pass through a coating machine. Such multilayer coating procedures are described, for example, in U.S. Pat. Nos. 2,761,791 and 3,508,947. These multilayer coating procedures often result in savings of time, effort, and expense in the coating of photographic elements. When such multiple wet layers are coated and dried, however, the matting agent particles can be forced into the emulsion layer of the element.
When such an element is imagewise exposed and processed, the image density in the area underlying a matting agent particle that has invaded the emulsion layer is diminished compared to other areas of the emulsion that have received equivalent exposure. These areas of decreased image density appear as small spots in the image. The resulting visual effect has been called the "starry night" effect due to the similarity in appearance to a starry night sky.
The problem of migration of soluble dye throughout the photographic element can be avoided by use of a filter dye layer overlying the emulsion layer in which the dye is immobile, for example, a solid particle dispersion dye. The use of such immobile dye layers in graphic arts films is described, for example, in U.S. Pat. No. 4,904,565, issued Feb. 27, 1990. Since the dye is connected in a layer above the emulsion, the light is uniformly filtered before it reaches the emulsion layer and the result is substantial improvement in contrast and reduction in speed variability. However, if matte particles are incorporated in the immobile dye layer, they tend to displace the dye upon drying of the layer. Thus, for example, the matte particles typically have a size of one to twenty microns, while the immobile dye layer may have a thickness of only one micron. Displacement of the dye by a matte particle causes the region of the emulsion layer directly beneath the matte particle to receive more exposure than occurs in areas where there are no matte particles. This problem of dye displacement is hereinafter termed "matte punch through". In a reversal film, the practical significance of this is that, when the photographic element is subjected to sufficient low level room light, areas under matte particles are exposed while areas not under matte particles are not exposed. Upon processing, the exposed areas clear out while the unexposed areas remain at maximum density. The appearance is the same as "starry night" effect.
It is toward the objective of providing an improved photographic element which avoids both the problem of dye migration and the problem of "matte punch through" that the present invention is directed.